The present invention relates to a control system for a robotized gearbox for a motor vehicle.
Gearboxes of this so-called xe2x80x9crobotizedxe2x80x9d type make it possible, by means of electro-mechanical or electro-hydraulic devices, to change the transmission ratio of a conventional manual gear box for example of a type using gears, or to change the drive selection of an automatic gearbox.
Robotized gear boxes with electro-mechanical actuators have become more widely used recently, since they involve fewer installation problems and are competitive as far as costs are concerned when compared to gearboxes with electro-hydraulic devices.
Typically, the actuator devices used in a robotized gearbox of an electro-mechanical type include geared motors, comprising an electric motor and an associated reduction gear which could belong to one of several known types, involving a nut and screw, a rack or a cam, for example, for converting the relative movement of the output shaft of the associated motor into a linear motion. Such geared motors are coupled to control levers of the gearbox by motion transmission devices. Typically, the transmission devices which are used can be either of a type using a Bowden cable or one using a rigid rod. Such transmission devices make it possible to isolate the control electronics, thereby reducing the demands made on the electronics system, from the point of view of heat, mechanical vibrations and environmental protection.
The aforesaid actuators of an electro-mechanical type are typically controlled by Pulse-Width-Modulation (PWM) signals and must have a braking system, since the increased resistance of the cables between the electronics system and the actuator devices can make the motors brake less efficiently.
In the prior art, robotized gear boxes also include a certain number of sensors, for determining the absolute positions of the gear lever members required for scanning all the operating positions corresponding to the various speed ratios or gears.
In the case of a conventional mechanical gearbox, using gears, the gears are operated by two lever members. A first lever member, known as the selector member, is needed to choose or select the line or xe2x80x9cplanexe2x80x9d (selection plane) of the gear to be engaged, and a second lever member (known as the engagement lever) is provided actually to engage the chosen gear.
One problem which is encountered with robotized gearboxes relates to determining the effective engagement position of the various ratios or gears at the end of the production line. A gearbox normally has rather high mechanical tolerances, making it necessary, at the end of the assembly line, to carry out calibration and/or adjustment operations in order to determine the actual position of the various speed ratios or gears accurately.
These calibration and/or adjustment operations constitute a disadvantage.
One object of the present invention is to provide a control system for a robotized gearbox which overcomes this disadvantage.
This and other objects are achieved according to the invention by providing a control system for a robotized gearbox having the characteristics which are described in the appended Claim 1.